1. Field of the Invention
The present invention relates to an image processing apparatus such as a host computer for transferring image information or an image output apparatus for forming images in accordance with image information.
2. Related Background Art
In a system in which a host computer is connected to a printer, one image output method is to transfer to the printer the program of a page descriptor language (to be abbreviated as a PDL hereinafter) formed by an application or the like of the host computer, develop the PDL into a bit image by a controller of the printer, and send the bit image to a printer engine, thereby outputting an image.
In the above method, in order to paste a natural image read by a scanner or the like into a line drawing described by, e.g., a graphic instruction of the PDL, information indicating the natural image is transferred as a file independently of the program of the PDL, and the program of the PDL containing a command for specifying the file and a command for specifying a position in which the natural image is to be pasted is transferred to the printer. The printer executes the pasting processing by decoding these commands.
Another output method is to develop the PDL into a bit image in the host computer and transfer the bit image to the printer, thereby outputting an image without executing any processing in the printer. This method requires, in the host computer, a CPU with a satisfactory processing capability, a memory with a large capacity, and a hard disk with a capacity large enough to temporarily store the developed bit image. An I/F with a speed high enough to send a bit image with a large capacity is also necessary between the host and the printer.
In order to paste the natural image into the line drawing by this method, the host computer holds information representing the natural image as a file and decodes the program of the PDL including a command for specifying the file and a command for specifying a position in which the natural image is to be fitted, thereby generating a bit map image in which the natural image is pasted in the line drawing. The bit map image thus formed is transferred to the printer.
The former method, however, has a drawback that the cost of the printer as a whole increases because the controller is incorporated.
The drawback of the latter method, on the other hand, is that the host computer is required to have a high processing ability, and a frame buffer for storing a bit image of one page is sometimes necessary on the printer side unless a special I/F with a very high transfer rate is used. This results in a very high cost of the memory. In order to transfer image data by using an I/F with a low transfer rate without providing any printer buffer on the printer side, a bit map image formed by the host computer may be compressed before being transferred to the printer and then expanded on the printer side. There has been proposed, however, no method of preferably compressing an image in which a natural image is pasted in a line drawing.
It is an object of the present invention to eliminate the drawbacks of the above conventional techniques and provide an image processing apparatus capable of transferring image information at a high efficiency.
In order to achieve the above object, an image processing apparatus of the present invention is characterized by comprising output means for outputting image information to be used in editing and area information for performing editing by using the image information, and transmitting means for transmitting the image information and the area information output from the output means, wherein the output means outputs the area information developed for each image in the form of compressed data.
In addition, an image processing apparatus of the present invention is characterized by comprising generating means for generating first image information representing a natural image, second image information representing a line drawing, and area information for performing editing by using the first image information and the second image information, and encoding means for synthesizing the second image information and the area information generated by the generating means and encoding the synthesized information.
Furthermore, an image processing apparatus of the present invention is characterized by comprising a host computer for processing image information, and a printer for forming a visible image of the image information processed by the host computer, wherein the host computer performs irreversible compression for image information representing a natural image in units of pixels and reversible compression for image information representing a line drawing in units of pixels, and transmits the compressed image information to the printer.
According to the present invention, in decoding and developing a page descriptor language containing a paste command for image information (to be referred to as to-be-pasted image information hereinafter) compressed as a file by irreversible coding or the like, this page descriptor language is developed into image information (i.e., line drawing information to be referred to as image information subjected to pasting with the to-be-pasted image information hereinafter) in a form not pasted with the above to-be-pasted image information. The image information subjected to pasting with the to-be-pasted image information can be compressed at a high efficiency by the irreversible coding. The to-be-pasted image information is compressed at a high efficiency with little image degradation by the irreversible coding.
The to-be-pasted image information and the image information subjected to pasting with the to-be-pasted image information, therefore, can be transferred efficiently because they are transferred separately.
A command contained in the page descriptor language program and indicating a position at which the to-be-pasted image information is to be pasted includes write start position information (a point at the upper right corner of the to-be-pasted image information), lateral width information, and longitudinal width information. A layout plane in the form of a bit map is formed by decoding these pieces of information. This layout plane can be compressed at a high efficiency by the same irreversible coding as of the image information subjected to pasting with the to-be-pasted image information.
If, therefore, a common encoding circuit is used time-divisionally, the image information subjected to pasting with the to-be-pasted image information and the layout plane can be encoded without providing any additional encoding circuit.
Other objects, advantages, and effects of the present invention will become apparent from the accompanying drawings, the following detailed description, and the appended claims.